The present invention relates to a method for reclaiming and reusing a wafer, and more particularly to a method for reclaiming and reusing a dummy wafer.
In the semiconductor industry, the wafer for controlling the stability of batch-to-batch fabrication is called a control wafer, and the wafer for maintaining the stability of single-batch fabrication is called a dummy wafer. For example, in order to control the stability of a machine, the wafer for non-productive purposes (e.g., usually bare silicon wafer) and the wafer for productive purposes are often put into the machine together during the polysilicon deposition process. By measuring the thickness of the polysilicon deposited on the wafer for non-productive purposes, the stability of fabrication (e.g., deposition rate, film property, and so on) can be controlled, and such kind of wafer for non-productive purposes is the so-called control wafer. Moreover, in order to maintain the quality of single-batch fabrication (e.g., the thickness uniformity of film), the wafer for non-productive purposes and the wafer for productive purposes are put into the boat together. Through filling these wafers for non-productive purposes in the boat, the product can be deposited stably and uniformly on the wafer to maintain the stability of single-batch fabrication when the reactive gas reacts in the furnace, and such kind of wafer for non-productive purposes is the so-called dummy wafer. Sometimes the used control wafer can be used as the dummy wafer.
The dummy wafer should be discarded or reclaimed after it has been reused many times; otherwise, the film will be peeled off from the dummy wafer due to the high stress of the film on the dummy wafer, which can cause severe pollution in the single-batch fabrication. The “reclaiming process” is to remove the film to acquire the bare silicon wafer. The reclaimed wafer can then be used as a control wafer or a dummy wafer.
For the over-reused dummy wafer, the reclaiming process is to directly remove the whole film by the grinding method, but this method will polish the wafer to the underside of the silicon substrate, so that the wafer will become thin and easy to break; besides, the outer annular portion of the film of the wafer may not be polished in some cases. Moreover, a wet etching method can also be used to directly remove the whole film. However, for the dummy wafer that is deposited with polysilicon, for example, since the etchant is used to remove the polysilicon layer, it will continue to etch the silicon wafer and cause the wafer to become thin and easy to break. Furthermore, if the availability of the etching or polishing machines is limited, the dummy wafers cannot be reclaimed as control wafers immediately, so the manufacturers need to additionally buy new wafers in response thereto.
Therefore, there is a need to develop a new method for reclaiming and reusing a wafer to overcome the aforesaid problems and difficulties in the prior art.